Plumbing terms that come up
- Trap
- The curved section of pipe under a fixture or below a floor drain that holds water. That water seal blocks sewer gas from rising into the room.
- Trap primer
- A device in some homes that adds water to a floor drain trap automatically. Many older homes do not have one.
- Cleanout
- A capped access point on a drain line used for clearing clogs. A loose or missing cap is an open path for sewer gas.
- Vent stack
- The pipe through the roof that lets the drain system breathe. A blocked vent can pull trap water out and let odor in.
- Sewer lateral
- The private line running from the house to the public sewer main. Older clay laterals can crack or be invaded by roots.
- Sewer scope
- A camera inspection of the lateral. Many Denver-area buyers order one during inspection, especially for older homes.
Working out which problem you have
- IfSmell disappears after pouring water into the floor drainThenThe trap was dry. Refill it regularly while the house is listed, and ask a plumber about a trap primer or trap seal insert if it dries quickly.
- IfSmell continues with a full trapThenCheck the cleanout cap near the drain or main stack. A loose or cracked cap is a quick plumber fix.
- IfSmell is worst when other fixtures drain, or toilets gurgleThenSuspect a vent issue or a partial blockage in the main line. Call a plumber.
- IfWater or debris has backed up into the drainThenStop using the plumbing and call a plumber. Sewage backups need proper cleanup, not deodorizing.
- IfSmell is around a toilet base rather than a drainThenA failed wax ring is likely. The toilet needs to be pulled and reset.
Why it is worth settling before listing
In many metro Denver neighborhoods built before the 1970s, buyers' agents routinely suggest a sewer scope, because older laterals can crack, separate or fill with roots. If a buyer walks into a basement that smells of sewer, that scope becomes much more likely and the buyer arrives at it already worried. Sellers sometimes choose to order their own scope before listing so they know what the camera will show; ask your agent whether that makes sense for your house.
A dry trap is the most likely cause in a basement drain that is rarely used, and it is also the easiest to overlook once the house is empty. Floor drains near furnaces and water heaters often go months without water reaching them, and Denver's dry indoor air pulls the seal down faster than people expect. Pouring a bucket of water in, waiting a day and checking again tells you a great deal for almost no effort.
If the drain turns out to be fine and the smell persists, do not reach for fragrance. A persistent sewer odor that resists the simple fixes is a plumbing question, and the answer may matter to a buyer.
Common questions
- Can I pour something in the trap to slow evaporation?
- Some plumbers suggest a small amount of mineral oil on top of the water, and trap seal inserts exist for drains that dry quickly. Ask a plumber what suits your drain.
General information for the Denver area, not a quote or professional advice. In an emergency, call 911.